Gorgoroth and Mount Doom.
The Hobbits scrambled down into the trough and soon found the Orc path which wound down from Cirith Ungol. The trough was probably a bit higher than the plain, say some 750 feet above sea level. At the point where the Hobbits climbed to the top of the Morgai and looked east, they were 1,500 feet above the plain (i.e. some 2,000 feet above sea level).They were then 40 miles from Orodruin and immediately above one of the Orc camps. The distance from the bridge to the junction of the road past the Orc camp and the road to Durthang was about 60 miles, and from that junction to Orodruin it was also 60 miles.
At Isenmouthe, which was some 20 miles east of there, the Hobbits slipped off the road and passed along the trench and earthwell which joined the spurs of Ephel Duath and Ered Lithui, about a furlong south of the road. From here the mountain appeared to be about 50 miles away.
Three roads met there, the western road to Durthang, the centre road which led south to join the road running up the eastern side of the Morgai, and the eastern road which wound south-east to Barad-dur. (The Land of the Shadow; Mount Doom; Bk 3)
The Hobbits followed this eastern road for four days until the mountain was almost due south of them, and, about 15 miles away. By this time they were not doing more than about 10 miles a day, and on the final stretch, going south, they were moving even more slowly and it took them two days to reach the foot of the Mountain. (Mount Doom; Bk 3).